1. Field of the Invention
This invention relates to a system for the selection of integrated circuits which are characterized by high reliability.
A system of this type serves to select integrated circuits for ensuring high-reliability application and is based on the principle known as dynamic burn-in testing, in which a selection is effected as a function of severe thermal and dynamic stresses. The equipment induces accelerated aging of components and failure of those components which are not capable of withstanding the stresses applied during the test. The other components which conform to the desired standards will thus be selected for the fabrication of equipment units which exhibit a minimum failure rate and therefore a high degree of reliability.
2. Description of the Prior Art
A selecting system comprises a set of bidirectional power amplifiers for exciting separate groups of integrated circuits of different types placed within a heat treatment chamber. The invention relates in particular to means for controlling the power amplifier unit. Current designs for this purpose are based on hardware which utilizes wired logic as a function of the type of integrated circuit to be selected or, in more recent versions, a logic system for generating stimuli which are stored in a programmable memory (PROM). This makes it necessary to set up a specialized department for studies, in parallel with the department concerned with the production of high-reliability circuits. The role of this study department is to carry out an extensive analysis of logic diagrams and excitation chronograms with respect to each type of integrated circuit. The result deduced by the department takes the form either of instructions for assembly and short-circuit wiring (straps) to be formed on matrix boards or of a binary program to be loaded in a PROM memory. The matrix circuits or loaded PROM memories must then be stored and managed as the integrated circuit selection process takes place.
A scheme of this nature must remain fairly rigid since any modification of circuit specifications at the user's request, or any change in standard circuit specifications, or any creation of a new technological family of integrated circuits, necessarily entails a substantial workload which in turn produces a delay in the performance of the selection. Furthermore, it may be considered that the work of analysis mentioned earlier is duplicated to no purpose with the work already performed by the programming department on an automatic integrated circuit tester within the scope of acceptance tests on the user's premises.
A further drawback results from the heat which is released by the integrated circuits to be selected and which gives rise to a disturbance of thermal equilibrium within the oven, thus entailing the need for relatively complex regulating circuits.